EP0241426B1 - Procédé et dispositif de coulée sous pression - Google Patents

Procédé et dispositif de coulée sous pression Download PDF

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Publication number
EP0241426B1
EP0241426B1 EP19870810211 EP87810211A EP0241426B1 EP 0241426 B1 EP0241426 B1 EP 0241426B1 EP 19870810211 EP19870810211 EP 19870810211 EP 87810211 A EP87810211 A EP 87810211A EP 0241426 B1 EP0241426 B1 EP 0241426B1
Authority
EP
European Patent Office
Prior art keywords
gas
impression
die
casting
mold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP19870810211
Other languages
German (de)
English (en)
Other versions
EP0241426A1 (fr
Inventor
Gunther Wulff
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcan Holdings Switzerland AG
Original Assignee
Schweizerische Aluminium AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Schweizerische Aluminium AG filed Critical Schweizerische Aluminium AG
Publication of EP0241426A1 publication Critical patent/EP0241426A1/fr
Application granted granted Critical
Publication of EP0241426B1 publication Critical patent/EP0241426B1/fr
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
    • B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
    • B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B22D17/14—Machines with evacuated die cavity
    • B22D17/145—Venting means therefor

Definitions

  • the invention relates to a method for producing void-free castings from metals or their alloys by pressing the melt under high casting pressure into a mold cavity, the metal being kept under pressure during solidification.
  • a method for producing void-free castings from metals or their alloys is known from DE-C-432 698.
  • a die casting system for producing void-free castings from metals or their alloys which comprises the following parts: at least two molded parts with mold parting surfaces forming a mold cavity; a filling chamber opening via a gate into the mold cavity and at least one bore opening into the mold cavity, into each of which an ejector pin is inserted.
  • Die casting is a widespread, inexpensive method of producing finished parts from molten metal in one operation. At most, these require little post-processing.
  • the process is used in particular for the casting of aluminum, magnesium, copper and zinc and their alloys and is especially preferred for thin-walled parts with complex shapes.
  • Gases present in the mold cavity during the mold filling process lead, among other causes, to pores in the solidified workpiece. Such pores reduce the quality of the products and thus significantly restrict the area of application of die-cast parts.
  • the origin of the gases is diverse: 1) When the machine is opened to remove the die-cast parts, the mold cavity fills with air. 2) To prevent the casting from sticking to the mold, the mold cavity must be periodically coated with a release agent. The constituents of these release agents, or their application aids, which are volatile at the temperature of the melt, form gases. 3) Lubricants must be used especially in the area of the filling chamber. Vapors from this also get into the mold cavity.
  • DE-C-2 517 140 discloses a die-casting process in which the air is first displaced from the mold cavity by flushing with a gas that is highly reactive with the molten metal to be cast, and then the molten metal is pressed into the mold cavity filled with the gas and after a time of 1 to 3 seconds after the end of the injection of the molten metal, but before the expiration of a certain time, which depends on the die casting thickness, an injection rod is driven into the mold cavity at a pressure of 50 to 300 MPa.
  • the injection rod is located at a suitable location in the mold and is driven into the still molten part of the casting by passing it through the solidified part on the surface of the injected molten metal, or by a solidified part of the surface of the injected melt by the action of the driven insertion rod is pressed into the molten part. Shrinkage cavities in the vicinity of the press-in rod can thus be almost completely avoided. If the casting has several larger thickenings, usually several press-in rods must be arranged. In order to be sufficiently effective, the press-in bars have to produce depressions which make up several% of the casting volume. This usually leads to a design of the casting blank, which requires extensive post-processing.
  • DE-C-452 698 discloses a die-casting process in which high pressure is exerted on the still liquid metal immediately after the mold is filled and is maintained until the casting has completely solidified.
  • the solidification process is conducted in such a way that the pressure introduction point remains fluid for the longest time.
  • US-A-3 420 291 discloses a method in which the metal is poured into a mold made of gas permeable ceramic.
  • the casting mold is located in a container, which is sealed gas-tight after filling the mold and subjected to gas pressure until the metal has completely solidified.
  • the invention is therefore based on the object of developing a casting method and a die casting system of the type mentioned at the outset, by means of which voids occurring due to the solidification shrinkage are prevented even in the case of complicated casting molds and also in the case of alloys which are difficult to cast. Overflow channels and similar formations that are later to be separated from the cast part are to be avoided here.
  • the object is achieved according to the invention in that after the entire surface of the casting has solidified piece and of at least 10% of the casting volume, but before demolding, high-tension gas is introduced into the mold cavity and this is placed under a pneumatic pressure of at least 2 MPa, preferably 10 to 50 MPa.
  • This pressure which is exerted on the entire volume of the casting, suppresses the formation of voids at all points on the inside of the casting.
  • the gas pressure required depends essentially on the casting material used, the casting geometry and the temperature of the casting at the time the pressure is applied.
  • air or nitrogen can be used as the compressed gas.
  • the casting Before the casting solidifies completely, it is preferably started to introduce the high-tension gas into the mold cavity. The most favorable phase for this begins after solidification of 10 to 30% of the casting volume.
  • the high pneumatic pressure in the mold cavity should be maintained at least until the casting has completely solidified.
  • the pneumatic pressure also causes the gas to expand the space between the mold and the casting in such a way that the casting is largely prevented from sticking to the mold. This is achieved by the fact that the gas surrounds the casting from almost all sides, so that most of the casting surface no longer touches the mold after the gas pressure has been applied. As a result of the gas pressure, the mold halves are typically pushed apart a few hundredths of a millimeter. Decreasing the adhesive considerably increases the life of the mold.
  • the gas in the phase after the casting has completely solidified, when the pressurized space is open, the gas is expanded to a substantially lower pressure before entering the mold cavity. This cools the gas and is able to extract effective heat from the cast part.
  • the mold cavity in order to prevent gas pores, is advantageously evacuated to a gas pressure of less than 25 kPa, preferably less than 0.5 kPa, before the melt enters.
  • the object is achieved according to the invention in that at least one of the molded parts has at least one gas passage, which opens into the mold cavity and is connected at the other end to a high-pressure gas source via a valve, and in that a gas seal on the mold parting surfaces is provided it is appropriate that both when the molded parts are joined together and in a state in which the mold separating surfaces are spaced apart, the mold cavity is closed to the outside together with the mouth of the filling chamber through the gas seal.
  • the mold should no longer be closed off by the gas seal in such a region of the mold parting surface distance, which is required for the removal of the casting.
  • the mold cavity can thus be pressurized by means of a high-tension gas which is introduced into the mold cavity after the surface solidification of the casting.
  • At least one of the molded parts preferably has at least one gas drain hole which opens into the region enclosed by the gas seal and is provided with a drain valve at the other end. This drain valve is controlled according to the pressure and flow requirements.
  • the gas drain hole, as well as the gas passage serving the gas inlet, is expediently positioned in such a way that the greatest flow and thus the greatest heat extraction prevail, especially over the casting areas with the lowest surface / volume ratio. This counteracts the delay in cooling due to the early detachment of the casting from the mold according to the invention. This helps to minimize the time required for the die casting system per casting; the casting is usually removed from the mold when the temperature falls below about 150 ° C. below the solidus.
  • the mold parting surfaces are designed such that when the molded parts are joined together outside the mold cavity, but within the area enclosed by the gas seal, they leave at least one drain channel open, into which the gas drain hole opens.
  • the targeted placement of such drainage channels enables the gas flow to be optimized with regard to a rapid cooling of the casting before removal.
  • valve located between the high pressure gas source and the mold cavity is designed such that it can be brought to a throttle position in a controlled manner.
  • the mold cavity is advantageously evacuated before the melt enters in order to prevent gas pores.
  • the mold parting surfaces are designed in such a way that when the molded parts are joined together outside the mold cavity, within the area enclosed by the gas seal, they leave at least one suction channel open, which is separated from the mold cavity when the molded parts are joined together, and which each has an evacuation hole in one of the molded parts and connected to a vacuum connection via a suction valve. Thanks to the position of the gas seal according to the invention, the mold cavity can be evacuated even before the molded parts have been completely joined, if the mold separating surfaces are still a few mm apart. After the molded parts have joined together, when the melt enters the mold cavity, the evacuation hole and the suction channel are protected against melt entry without the use of an expensive shut-off valve.
  • the gas passage for the entry of the high-tension gas into the ejector pin and its bore is integrated.
  • This version relieves the form of additional, complex connections.
  • the ejector pin and the associated bore are cylindrical, with a truncated cone-like truncated cone on the cylinder, and that the cylindrical part of the ejector pin with a longitudinal groove for passage is part of the gas passage of the gas is provided.
  • the truncated cone ends on the mold cavity side with a surface that continuously continues the surrounding mold wall.
  • the cold chamber die-casting system shown in FIG. 1 comprises a movable molded part 1 and a fixed molded part 2, which form a mold cavity 3 when they are joined and meet the mold parting surfaces 4 and 5 outside of the latter.
  • the mold cavity 3 has a volume of 3 liters.
  • the width of the mold cavity 3 is for the most part 2.5 mm; widenings of up to 10 mm are provided in individual areas.
  • the fixed molded part 2 encloses the end of a filling chamber 14 which is connected to the mold cavity 3 via a gate 19 and via which aluminum melt of the AISi7Mg alloy is pressed into the mold cavity 3 by means of a pressure piston 24 with a pressure of approximately 70 MPa.
  • the mold cavity 3, together with the mouth of the filling chamber 14, is sealed gas-tight to the outside by a gas seal 9.
  • the gas seal 9 is designed as a sliding seal, and the molded parts 1 and 2 are formed in the area of the gas seal 9 in such a way that the gas seal 9 also closes to the outside when the molded parts 1 and 2 are not connected and the mold separating surfaces 4 and 5 are mutually exclusive Have a distance of 8 mm. In this state, the mold can already be evacuated to an air pressure of 0.4 kPa.
  • a suction channel 10 which is placed in a ring around the mold cavity 3 and runs within the gas seal 9, is used as a channel in the fixed molded part 2 and is covered by the molded parting surface 4 when the molded parts 1 and 2 are joined.
  • an evacuation hole 12 of the movable molded part 1 opens into this suction channel 10.
  • the evacuation hole 12 is connected to a vacuum connection via a suction valve 13.
  • the suction valve 13 remains open even after the combination of the two molded parts 1 and 2 until the aluminum melt has filled the mold cavity 3 and the resulting casting (not shown) has solidified over its entire surface.
  • the ejector pins 6 consist of a cylindrical and, on the mold cavity side, a frustoconical part. After cooling the aluminum casting to 400 ° C and opening the mold, they serve to eject the casting. A possible clearance between them and the ejector pins 6 is closed to the outside by a seal 23 at the outer mouth of the bores 11.
  • the cylindrical part of the ejector pins 6 - as shown schematically in cross section in FIG. 2 - is provided with a longitudinal groove 20.
  • the bores 11 are cut through a line 22 each, which lead to the outside and are each connected via an adjustable proportional valve 7 to a high-pressure gas source 8, which supplies nitrogen at 20 MPa.
  • a high-pressure gas source 8 which supplies nitrogen at 20 MPa.
  • the suction valve 13 is closed and the valves 7 opened.
  • nitrogen is pressed over the lines 22 and through the longitudinal grooves 20 and the frustoconical end of the ejector pins 6 is pressed slightly into the mold cavity 3, as a result of which a passage for the high-tension nitrogen opens in the frustoconical area between the ejector pins 6 and the bores 11.
  • the ejector pins 6 and the bores 11 each form a gas passage 15.
  • the nitrogen entering the mold cavity 3 puts the latter under a pneumatic pressure of approximately 20 MPa, has a compressing effect on the casting that has not yet solidified inside and presses the two molded parts 1 and 2 apart by about 0.1 mm, which further increases the space between the mold and the casting. This is enveloped by nitrogen on almost all sides, which largely prevents sticking to the mold.
  • the mold parting surface 5 of the fixed mold part 2 is formed in the area between the annular suction channel 10 and the mold cavity 3 in such a way that the mold part 2 has, in some areas, depressions which are covered by the mold parting surface 4 when the two mold parts 1 and 2 come together and form six drainage channels 21.
  • the movable molded part 1 has six gas drain holes 16 which open in the mold separating surface 4 in the region of the drain channels 21 and are each provided with a drain valve 17 at the outer end. These drain valves 17 are opened after the casting has solidified, approximately 3.5 s after the mold filling has been completed.
  • the proportional valves 7 are set to a throttle position, which reduces the pressure of the inflowing nitrogen to approximately 1 MPa.
  • the tensioned nitrogen in the mold cavity 3 then flows between the two mold parting surfaces 4 and 5 to the drainage channels 21 and reaches the outside via the drain valves 17.
  • the position of the drainage channels 21 relative to the mold cavity 3 and the setting of the drain valves 17 is chosen so that the nitrogen sweeps over the casting at the locations with strong flow, which require greater heat removal due to the unfavorable surface / volume ratio.
  • the casting can be cooled to the 400 ° C. at which the mold is opened and the casting is removed. After about 30 s, the casting is ejected. The casting is free of pores and voids even after the subsequent heat treatment.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)

Claims (10)

1. Procédé de fabrication de pièces de fonderie, en métaux ou en leurs alliages, sans retassures, par mise sous pression du bain de fusion, sous une pression de coulée élevée, dans un espace creux (3) de moule, étant précisé que le métal est maintenu sous pression pendant la solidification,
caractérisé en ce qu'après la solidification de l'ensemble de la surface de la pièce de fonderie et d'au moins 10 % du volume de la pièce de fonderie, mais avant le démoulage, on amène dans le volume creux (3) du moule du gaz sous haute pression et qu'on le met sous une pression pneumatique d'au moins 2 MPa, de préférence 10 à 50 MPa.
2. Procédé selon la revendication 1, caractérisé en ce que l'on amène le gaz sous haute pression dans le volume creux (3) du moule avant solidification complète de la pièce de fonderie et que l'on maintient la pression pneumatique élevée dans le volume creux (3) du moule au moins jusqu'à solidification complète de la pièce de fonderie.
3. Procédé selon la revendication 2, caractérisé en ce qu'après solidification complète de la pièce de fonderie, on ouvre l'espace qui est sous pression, en des endroits prédéterminés, pour évacuer le gaz, étant précisé que l'on choisit ces endroits de façon telle que les flux de gaz qui apparaissent dans l'espace creux (3) du moule se dirigent au-dessus des zones de la surface de la pièce de fonderie qui présentent un besoin élevé d'évacuation de chaleur; et en ce que de préférence on détend partiellement le gaz avant de l'envoyer dans l'espace creux (3) du moule.
4. Procédé selon au moins l'une des revendications 1 à 3, caractérisé en ce qu'avant l'introduction du bain de fusion, on met sous vide le volume creux (3) du moule en l'amenant à une pression inférieure à 25 kPa, de préférence inférieure à 0.5 kPa.
5. Installation de coulée sous pression pour la fabrication de pièces de fonderie, en métaux ou en leurs alliages, sans retassures, comportant au moins deux parties de moule (1, 2) formant un espace creux (3) de moule, avec des surfaces de joint (4, 5), une chambre de remplissage (14) débouchant dans l'espace creux (3) du moule par l'intermédiaire d'un étranglement (19), ainsi qu'au moins un perçage (11) qui débouche dans l'espace creux (3) du moule et dans lequel est chaque fois insérée une tige d'éjecteur (6),
caractérisée
en ce qu'au moins l'une des parties du moule (1, 2) présente au moins un passage de gaz (15) qui débouche dans l'espace creux (3) du moule et qui, à l'autre extrémité, est relié, par l'intermédiaire d'une vanne (7), avec une source de gaz sous haute pression (8); et en ce qu'une garniture d'étanchéité au gaz (9) est appliquée sur les surfaces de joint (4, 5) de façon telle qu'aussi bien lors de la fermeture des parties du moule (1, 2) que dans un état dans lequel les surfaces de joint (4) et (5) présentent une certaine distance, l'espace creux (3) du moule, ainsi que l'embouchure de la chambre de remplissage (14), sont rendus étanches à l'égard de l'extérieur par la garniture d'étanchéité au gaz (9).
6. Installation de coulée sous pression selon la revendication 5, caractérisée en ce qu'au moins l'une des parties du moule (1, 2) présente au moins un perçage d'évacuation des gaz qui débouche dans la zone enclose dans la garniture d'étanchéité (9) et, à l'autre extrémité, est munie d'une vanne d'évcuation (17).
7. Installation de coulée sous pression selon les revendications 5 et 6, caractérisée en ce que l'on peut ramener la vanne (7) à une position formant étranglement.
8. Installation de coulée sous pression selon la revendication 6 ou la revendication 7, caractérisée en ce que les surfaces de joint (4, 5) du moule sont conçues de façon telle que, lors de la fermeture des parties du moule (1, 2), à l'extérieur de l'espace (3) du moule, à l'intérieur de la zone enclose par la garniture d'étanchéité (9), elles laissent ouvert au moins un canal d'évacuation (21) dans lequel débouche le perçage (16) d'évacuation des gaz.
9. Installation de coulée sous pression selon au moins l'une des revendications 5 à 8, caractérisée en ce que les surfaces de joint (4, 5) du moule sont conçues de façon telle que, lors de la fermeture des parties du moule (1, 2), à l'extérieur de l'espace (3) du moule, à l'intérieur de la zone enclose par la garniture d'étanchéité (9), elles laissent ouvert au moins un canal d'évacuation (10) qui, lors de la fermeture des parties du moule (1, 2) est séparé de l'espace creux (3) du moule et qui est respectivement relié, par l'intermédiaire d'un perçage de mise sous vide (12), prévu dans l'une des parties (1, 2) du moule et par l'intermédiaire d'une vanne d'aspiration (13), avec un raccord (8) de mise sous vide.
10. Installation de coulée sous pression selon au moins l'une des revendications 5 à 9, caractérisée en ce que le passage (15) du gaz est incorporé dans le perçage (11) et dans la tige d'éjecteur (6), étant précisé que l'on préfère que la tige d'éjecteur (6) et le perçage (11) soient de forme cylindrique et qu'un tronc de cône se raccorde au cylindre, à la façon d'une trompette, côté espace creux du moule; et en ce que, en tant que partie du passage (15) des gaz, la partie cylindrique de la tige d'éjecteur (6) présente une rainure longitudinale (20).
EP19870810211 1986-04-11 1987-04-06 Procédé et dispositif de coulée sous pression Expired EP0241426B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CH1442/86 1986-04-11
CH1443/86 1986-04-11
CH144386 1986-04-11
CH144286 1986-04-11

Publications (2)

Publication Number Publication Date
EP0241426A1 EP0241426A1 (fr) 1987-10-14
EP0241426B1 true EP0241426B1 (fr) 1989-07-12

Family

ID=25687668

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870810211 Expired EP0241426B1 (fr) 1986-04-11 1987-04-06 Procédé et dispositif de coulée sous pression

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EP (1) EP0241426B1 (fr)
DE (1) DE3760303D1 (fr)

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2606688B1 (fr) * 1986-11-17 1989-09-08 Pechiney Aluminium Procede de moulage a mousse perdue de pieces metalliques
DE68903103T2 (de) * 1989-03-07 1993-04-15 Pechiney Aluminium Verfahren zum vollformgiessen von metallischen gegenstaenden unter druck.
JPH03230855A (ja) * 1990-02-05 1991-10-14 Yamazaki Kosakusho:Kk ダイカストの真空鋳造法
BR9605884A (pt) * 1995-03-20 1997-09-16 Thurner Bayer Druckguss Processo para fabricação de peças moldadas sob pressão
DE19605727A1 (de) * 1996-02-16 1997-08-21 Mueller Weingarten Maschf Vakuum-Druckgießmaschine
DE102004052231A1 (de) * 2004-10-27 2006-05-11 Ks Kolbenschmidt Gmbh Verfahren zur Serienherstellung von Kolben für Brennkraftmaschinen unter Gasdruckeinwirkung
DE102012023214B3 (de) * 2012-11-28 2014-04-03 Audi Ag Verfahren zur Herstellung eines metallischen Druckgussbauteils mit lokaler Gasinjektion zur Vermeidung von Erstarrungsporosität
DE102017109716B3 (de) 2017-05-05 2018-07-26 Tobias Beck Metall-Druckguss-Formwerkzeug
JP7215409B2 (ja) * 2019-12-19 2023-01-31 トヨタ自動車株式会社 鋳造方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE452698C (de) * 1923-12-02 1927-11-17 Ludw Loewe & Co Akt Ges Verfahren zur Herstellung von Gussstuecken unter Druck
CH302219A (fr) * 1952-02-07 1954-10-15 Hodler Fritz Procédé de fonte sous pression d'objets en métal et machine permettant la mise en oeuvre dudit procédé.
US3420291A (en) * 1965-12-29 1969-01-07 Trw Inc Method for reducing metal casting porosity
GB1199476A (en) * 1967-09-19 1970-07-22 Rolinx Ltd Injection Moulding.
FR2418049A1 (fr) * 1978-02-22 1979-09-21 Glazunov Sergei Installation a vide pour couler sous pression des ebauches metalliques
JPS54151513A (en) * 1978-04-27 1979-11-28 Leibfried Dieter Low pressure dieecasting of metal* particularly of ne metal and apparatus therefor

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Publication number Publication date
DE3760303D1 (en) 1989-08-17
EP0241426A1 (fr) 1987-10-14

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